Known apparatus used to treat substrates with ions include beamline ion implanters and plasma immersion ion implantation tools. These approaches are appropriate for implanting ions over a range of energies. In beamline ion implanters ions are extracted from a source, mass analyzed and then transported to the substrate surface. In plasma immersion ion implantation apparatus, a substrate is located in the same chamber the plasma is generated adjacent to the plasma. The substrate is set at negative potential with respect to the plasma and ions crossing the plasma sheath in front of the substrate impinge on the substrate at perpendicular incidence angle.
Recently a new processing apparatus facilitating control of extracted ion angular distribution (IAD) has been developed. In this apparatus ions are extracted from a plasma chamber where the substrate is located proximate the plasma chamber. Ions are extracted through an extraction aperture of special geometry located in an ion extraction optics placed proximate a plasma. To extract an ion beam having controllable and uniform properties, the extraction aperture may be elongated to generate an ion beam having the shape of a ribbon beam when ions are extracted from the plasma. For example, the ribbon beam may have a cross-section having a short dimension as small as a few millimeters, and a long dimension on the order 10 centimeters to 50 centimeters. By exposing a substrate to the ribbon beam and scanning a substrate with respect to the extraction aperture along a direction parallel to the short dimension, an entirety of a large substrate such as a 300 mm wafer may be exposed to ribbon beam.
In such an apparatus, to expose a substrate to a targeted dose of ions, the substrate may be scanned with respect to the extraction aperture at an appropriate velocity to allow each portion of the substrate to receive the targeted dose, given the ion density of the ribbon beam and the size of the ribbon beam. Throughput of substrate processing may accordingly be limited by the size of the extraction aperture along the short dimension, as well as the plasma density or ion density of a plasma chamber generating the ribbon beam. While in principle ion beam current of a ribbon beam delivered to a substrate may be increased by increasing parameters such as the power delivered to the plasma, the increase in power may increase plasma density and consequently undesirably change beam properties of the ribbon beam, such as the angle of incidence of ions or distribution of angles of incidence of the ions. Likewise, while in principle an aperture size along the short dimension of an aperture may be increased, the ability to manipulate and control the geometry of the ribbon beam when the short dimension is increased beyond a few millimeters to a few centimeters may be impractical. With respect to these and other considerations, the present disclosure is provided.